Struct NoArgs

pub struct NoArgs { /* private fields */ }

Indicates that an Ioctl does not take any arguments.

This is used as the type parameter of Ioctl by the _IO and _IOC functions. Ioctl<NoArgs> comes with its own, separate IOCTL.ioctl(fd) method that only takes the file descriptor as an argument.

Since NoArgs is the default value for Ioctl’s type parameter, it can typically be omitted.

Example

The uinput ioctls UI_DEV_CREATE and UI_DEV_DESTROY do not take any arguments, while UI_DEV_SETUP does take an argument.

From linux/uinput.h:

/* ioctl */
#define UINPUT_IOCTL_BASE	'U'
#define UI_DEV_CREATE		_IO(UINPUT_IOCTL_BASE, 1)
#define UI_DEV_DESTROY		_IO(UINPUT_IOCTL_BASE, 2)
...
#define UI_DEV_SETUP _IOW(UINPUT_IOCTL_BASE, 3, struct uinput_setup)

use std::{mem, fs::File, ffi::c_char};
use libc::uinput_setup;
use linux_ioctl::*;

const UINPUT_IOCTL_BASE: u8 = b'U';
const UI_DEV_CREATE: Ioctl<NoArgs> = _IO(UINPUT_IOCTL_BASE, 1);
const UI_DEV_DESTROY: Ioctl<NoArgs> = _IO(UINPUT_IOCTL_BASE, 2);
const UI_DEV_SETUP: Ioctl<*const uinput_setup> = _IOW(UINPUT_IOCTL_BASE, 3);

let uinput = File::options().write(true).open("/dev/uinput")?;

let mut setup: libc::uinput_setup = unsafe { mem::zeroed() };
setup.name[0] = b'A' as c_char; // (must not be blank)
unsafe {
    UI_DEV_SETUP.ioctl(&uinput, &setup)?;
    UI_DEV_CREATE.ioctl(&uinput)?;
    // ...use the device...
    UI_DEV_DESTROY.ioctl(&uinput)?;
}